1. Field of the Invention
The invention generally relates to dextran fibers, preferably electrospun dextran fibers, and devices formed therefrom. In particular, such devices may be bandages which include therapeutic substances associated with the electrospun fibers, which, upon exposure to a liquid that dissolves the electrospun fibers, are released into the liquid.
2. Background of the Invention
The body's natural response to stem bleeding from a wound is to initiate blood clotting via a complex process known as the coagulation cascade. The cascade involves two pathways that ultimately lead to the production of the enzyme thrombin, which catalyzes the conversion of fibrinogen to fibrin. Fibrin is then cross-linked to form a clot, resulting in hemostasis. For wounds that are not severe, and in individuals that have no countervening conditions, the body is usually able to carry out this process efficiently in a manner that prevents excessive loss of blood from the wound. However, in the case of severe wounds, or in individuals in whom the clotting mechanism is compromised, this may not be the case. For such individuals, it is however possible to administer components of the coagulation cascade, especially thrombin and fibrinogen, directly to the wound to bring about hemostasis. Bandaging of bleeding wounds is also a usual practice, in part to isolate and protect the wounded area, and also to provide a means to exert pressure on the wound, which can also assist in controlling bleeding.
While these methods may be carried out satisfactorily in cases of mild trauma or under conditions of “controlled” wounding (e.g. surgery), many situations in which such treatments are most needed are also those in which it is the most difficult to provide them. Examples of such wounds include, for example, those inflicted during combat, or unanticipated wounds that occur as the result of accidents. In such circumstances, survival of the wounded individual may depend on stopping blood loss from the wound and achieving hemostasis during the first few minutes after injury. Unfortunately, given the circumstances of such injuries, appropriate medical intervention may not be immediately available.
In particular, the treatment of penetrating wounds such as bullet wounds or some wounds from shrapnel is problematic. This is due to the difficulty in placing a bandage and/or therapeutic agents at the actual site of injury, which includes an area that is well below the body surface and difficult or impossible to access using conventional techniques.
Jiang et al. (Biomacromolecules 2004, 5, 326-333) teaches electrospun dextran fibers. Agents associated with the fibers (e.g. BSA, lysozyme) are directly electrospun into the fibers. The fibers may also include other polymers electrospun with the dextran.
Jiang et al. (2006, Journal of Biomedical Materials Research Part B: Applied Biomaterials, 50-57, Wiley Periodicals, Inc.) discloses electrospun fibers which are a composite of poly(c-caprolactone) as a shell and dextran as a core. These fibers provide the slow release of agents (bovine serum albumin, BSA) which are also electrospun into the fibers.
U.S. Pat. No. 6,753,454 to Smith et al. (Jun. 22, 2004) discloses electrospun fibers comprising a substantially homogeneous mixture of a hydrophilic polymer and a polymer which is at least weakly hydrophobic, which may be used to form a bandage. The bandage may comprise active agents (e.g. dextran). However, the disclosed fibers are not readily soluble in liquid.
U.S. Pat. No. 6,762,336 to MacPhee et al. (Jul. 13, 2004) teaches a hemostatic multilayer bandage that comprises a thrombin layer between two fibrinogen layers. The bandage may contain other resorbable materials such as glycolic acid or lactic acid based polymers or copolymers. Neither electrospun fibers nor dextran fibers are taught as components of the bandage.
U.S. Pat. No. 6,821,479 to Smith et al. (Nov. 23, 2004) teaches a method of preserving a biological material in a dry protective matrix, the matrix comprising fibers such as electrospun fibers. One component of the fibers may be dextran, but homogeneous dextran fibers are not described.
U.S. Pat. No. 7,101,862 to Cochrum et al. (Sep. 5, 2006), teaches hemostatic compositions and methods for controlling bleeding. The compositions comprise a cellulose containing article (e.g gauze) to which a polysaccharide is covalently or ionically crosslinked. The crosslinked polysaccharide may be dextran. However, the compositions are not electrospun and exogenous clotting agents are not included in the compositions.
United States patent application 2004/0018226 (Wnek et al., published Jan. 29, 2004) discloses fibers produced by an electroprocessing technique such as electrospinning. The fibers comprise enclosures within the fibers for containing substances that are not miscible with the fibers. Dextran is not taught as a fiber component.
United States patent application 2007/0160653 (Fisher et al., published Jul. 12, 2007) teaches a hemostatic textile comprising hemostatic factors (e.g. thrombin, fibrinogen) but the fibers are formed from electrospun glass plus a secondary fiber (e.g. silk, ceramic, bamboo, jute, rayon, etc.)
United States patent application 2008/0020015 (Carpenter et al., published Jan. 24, 2008) teaches wound dressing comprised of various biodegradable polymers and hydrogels having allogenic or autologous precursor cells (e.g. stem cells) dispersed within the polymers. The polymers may be prepared by electrospinning, and one polymer component may be dextran. However, the polymers cannot be immediately soluble upon contact with liquid, as they must provide a scaffolding for delivery of the cells over time, even though the polymers eventually biodegrade in situ.
United States patent application 2008/0265469 (Li et al., priority date: Nov. 10, 2006) describes electrospun nanofibers which may comprise dextran. However, the nanofibers are not described as readily soluble in liquids.
United States patent application 2009/0053288 (Eskridge et al., published Feb. 26, 2009) teaches a woven hemostatic fabric comprised of about 65% fiberglass yarn and about 35% bamboo yarn. The fiberglass component may be electrospun, and hemostatic factors such a thrombin may be associated with the fabric, e.g. by soaking the material in a solution of thrombin. Dextran may be added as a hygroscopic agent.
There is an ongoing need to provide improved methods and means to initiate blood clotting in wounds in order to stop or at least slow blood loss. In particular, there is an ongoing need to improve the capability to readily promote hemostasis in severe wounds in a facile manner, especially under circumstances where immediate treatment by medical personnel is limited or unavailable.